1. Field of the Invention
This invention relates to automated methods and apparatus for making beaded dental floss, wherein the beads must be firmly fixed to the floss and located thereon with precision.
2. Description of the Prior Art
Beaded or knotted dental floss is known in the art. U.S. Pat. No. 3,631,869 "Dental Floss Holder" to R. J. Espinosa states (column 2, line 31) "The nubs 1 (on the floss) could constitute drops of hardened material applied in liquid form to a straight, smooth floss. Alternatively, the nubs 1 could comprise pronounced crimps which have been mechanically imparted to normally straight floss fiber or they could even comprise clips applied to the floss mechanically." U.S. Pat. No. 3,974,842 "Disposable Flosser" to I. S. Chodorow states (column 6, line 30) " . . . beads . . . knots, loops or other enlargements of the floss itself. . . . Beads may be fastened onto the floss by mechanical crimping, or cementing, or any feasible method. A simpler technique would be to simply place a drop of cement or appropriate solvent at 32 where the floss extends . . . or a bead or knot at 32." U.S. Pat. No. 1,815,408 "Dental Floss Holder" to J. K. Jordan refers to "knots" on the dental floss. U.S. Pat. Nos. 4,753,254 and 4,776,357, granted to the present inventors, also mentions beaded dental floss.
However, all of these patents are directed primarily toward floss applicators, treating the beaded floss almost as an incidental accessory. Hence, none of them teaches or claims methods or apparatus for making beaded floss, or cites specific materials from which the beads or enlargements on the floss can be made. Therefore, considerable experimentation and inventing would be required in order to actually manufacture beaded floss on the basis of teachings in the cited patents.
As mentioned above, two of the prior-art patents teach knots in the floss as being equivalent to beads in effectiveness. However, no particular kind of knot is specified, nor is it indicated how such a knot would be tied. In the present inventors' experiments, it was observed that knots are inherently asymmetric, and, hence, somewhat more conducive to tangling the floss that is the case with small, symmetrical beads. Also, it is not disclosed how the crimps, as mentioned in the Espinosa patent, would work. It would seem that crimps would simply straighten out when the floss is placed under tension. Also, his hardened material that can be applied to the floss in liquid form leaves many questions, such as: What materials would be used with what kind of floss that would provide the required strength of adhesion? What liquid material would form a bead, rather than simply wick into the floss? How would one form a symmetrical bead on the floss with liquid material?
The "mechanical crimping" of beads, cited in the Chodorow patent, seems to imply metallic beads. This would suggest the possibility of cutting the floss accidentally in the process of such crimping. Similarly, the cementing of beads to the floss, cited in the Chodorow patent, would require experimentation to discover an appropriate cement and bead material that would serve the required purpose, and means for positioning the beads on the floss.